Mammalian CNS neurons have a negligible capacity to regenerate following lesion or acute ischemic (no oxygen supply) conditions. A dramatic decrease or complete abolishment of oxygen supply to the nerve cells and other cells in a certain region of the brain can occur due to occlusion of one or more of the arteries that supply blood to the brain (Fisher M., “Characterizing the Target of Acute Stroke Therapy”, Stroke, Vol. 28 No 4 pp. 866-872 April 1997). Concomitantly with this event, the neurons of the brain go through a gradual degeneration process that eventually leads to necrosis in the acute ischemic zone. Clinical syndromes such as paraplegia, quadriplegia, etc., are evident due to dysfunction of the nerve cells in the brain.
The mammalian CNS also has a negligible capacity to regenerate following injury. Limited regeneration of peripheral axons in mammals and CNS in lower vertebrate can take place in a post trauma setting.
Low energy laser irradiation has recently been found to modulate various processes in different biological systems, (Belkin et al, A critical review of low energy laser bioeffects. Lasers Light Ophthalmology vol. 2 p. 63-71, 1988 and Conlan et al, Biostimulation of wound healing by low energy laser irradiation, Journal of Clinical Periodontology vol. 23, p. 492-496, 1996). The effect of low energy laser irradiation following trauma has been investigated so far in skin, peripheral nerves and skeletal muscles.
Assia et al (Temporal parameters of low energy laser irradiation for optimal delay of post traumatic degeneration of Ito rat optic nerve, Brain Research 476: 205-212, 1989) described the possibility of delaying the post traumatic process of degeneration and scar tissue formation of a crushed optic nerve (peripheral nervous system) by low energy laser irradiation.
U.S. Pat. No. 5,580,555 to Schwartz involves the administration of tumor necrosis factor (TNF) to the sight of injury in the optic nerve in order to facilitate regeneration of axons across the sight of the injury. The use of low energy laser in conjunction with the use of the TNF is suggested to augment the effect of TNF. However, Schwartz presents no experimental results to favor the beneficial effect of the laser. Furthermore, it is described in the detailed description that treatment with TNF alone (without laser irradiation) gives good results.
It has previously been suggested that regeneration of injured peripheral nerves can be accelerated by LEL (Rochkind S. Stimulation effect of laser energy on the regeneration of traumatically injured peripheral nerves. The Krim National Medical Inst. Morphogenesis and Regenerations Vol. 73: pp. 48-50, 1978) Nissan M. Rochkind S. et al (HeNe laser irradiation delivered transcutaneously: its effect on sciatic nerve of rats. Laser. Surg. Med. Vol. 6: pp. 435-438, 1996) also demonstrated that transcutaneous LEL of sciatic nerve induced an increase in the amplitude of the electrical signals recorded in the irradiated nerve, i.e. increased the size of the action potential.
U.S. Pat. No. 4,966,144 to Rochkind et al deals with a method of inducing functional regeneration of nerve fibers of an injured sight of the spinal cord (or using grafts of peripheral nerves which were placed into the injured sight) by a light source which generates light at a wavelength of 330-1200 nm. The method involves only the spinal cord but not the brain. Moreover, the method is not related to an acute ischemic phase of nerve cells in the CNS as in a situation of “stroke” nor is the cytoprotective effect of laser irradiation cited in Rochkind et al.
It has previously been reported that the low energy laser irradiation causes a decrease in the inflammatory response following injury to skeletal muscles (Bibikova A. & U. Oron. Promotion of muscle regeneration following cold injury to the toad (Bufo Viridis) gastrocnemius muscle by low energy laser irradiation. Anat. Rec. (1993) vol. 235 pp. 374-380 and N. Weiss & U. Oron Enhancement of muscle regeneration in the rat gastrocnemius muscle by low energy laser irradiation. Anat. Embryol. (1992) Vol. 186 pp. 497-503). The above phenomenon may suggest possible cytoprotective effect of at least the mitochondria and maybe other structures of the cell by the LEL. Thus. LEL irradiation allows cells under stressful conditions of low or no oxygen supply to maintain their viability in spite of the harsh conditions. The irradiated cells most probably do not degenerate to the same extent as the non-irradiated cells and therefore also the inflammatory response, which is typical to tissues undergoing a degenerative process following injury is markedly decreased. Furthermore, LEL irradiation has been found to enhance the process of formation of new blood vessels (angiogenesis) in injured skeletal muscles (Bibikova A. Belkin A. and Oron U. Enhancement of angiogenesis in regenerating gastrocnemius muscle of the toad, (Bufo Viridis) by low energy laser irradiation. Anat. Embryol. (1994) Vol. 190 pp. 597-602).
So far, despite significant research efforts for many years worldwide, a safe and effective method of inhibiting or eliminating the adverse irreversible effects of stroke and other ischemic events on brain cells and the significant clinical manifestations of it on animal and human body function has vet to be developed.